Don't hardcode the list of events types in fn

sky/examples/fn/widgets/menuitem.dart

 part of widgets;
 
 class MenuItem extends ButtonBase {
 
   static Style _style = new Style('''
     transform: translateX(0);
     display: flex;
     align-items: center;
     height: 48px;
     -webkit-user-select: none;'''
@@ skipping 15 matching lines @@
   static Style _labelStyle = new Style('''
       font-family: 'Roboto Medium', 'Helvetica';
       color: #212121;
       padding: 0px 16px;
       flex: 1;'''
   );
 
   List<Node> children;
   String icon;
 
-  sky.EventListener onClick;
-
-  MenuItem({ Object key, this.icon, this.children, this.onClick }) : super(key: key) {
-  }
+  MenuItem({ Object key, this.icon, this.children }) : super(key: key);
 
   Node render() {
     return new Container(
       style: _highlight ? _highlightStyle : _style,
-      onClick: onClick,
-      onPointerDown: _handlePointerDown,
-      onPointerUp: _handlePointerUp,
-      onPointerCancel: _handlePointerCancel,
       children: [
         super.render(),
         new Icon(
           style: _iconStyle,
           size: 24,
           type: "${icon}_grey600"
         ),
         new Container(
           style: _labelStyle,
           children: children
         )
       ]
     );
   }
 }